1. Field of the Invention
This invention relates to a magnetic head device to be incorporated in a hard disc drive which is an external memory device for computers, and more particularly, to a magnetic head device with a constant head floating height which is structured to make the amount of floating of a head slider raised from a hard magnetic disc, when driven, substantially constant over the whole area of the memory/reproducing region of the disc.
2. Discussion of the Background
In a hard disc drive device for recording/reproducing digital information by means of a magnetic disc of a rigid material, a slider of a magnetic head is held at the tip end of a suspension means (a load beam) extending from a head arm, the base of said arm is fixed on a swinging shaft (an arm drive shaft) near the outer periphery of the magnetic disc, and the magnetic head at the tip end of the suspension means is rotated substantially radially about the said arm drive shaft which is used as a fulcrum so as to perform seeking of the recording track on the disc. During recording/reproducing, the head slider slightly floats over said magnetic disc by air pressure generated between an air bearing surface of the magnetic head opposing the disc and the rotating disc. As fluctuation in floating height affects recording/reproducing characteristics during operation, it is necessary to make the height of floating constant over the whole area that the head slider seeks in order to obtain excellent characteristics. There have been proposed in the prior art various methods to make the floating height constant. For example, the related art shows a load applied on the slider to press the magnetic disc by means of the suspension means. Another related device sets the area, particularly the width, of the air bearing surface smaller in the direction perpendicular to the direction of disc traveling.
The peripheral speed of a magnetic disc of a hard disc drive device, when rotated, is generally higher on the outer periphery than the inner periphery, and therefore, the air pressure between the air bearing surface of said head slider and said magnetic disc is higher at the outer periphery. As the speed of rotation of such magnetic discs has increased in recent years, fluctuations in the height of the floating head slider in the radial direction of the disc cannot be controlled by merely applying a larger load on the head slider or setting a smaller width for the air bearing surface. Especially, with the recent increase in the packing density, head sliders are required to have lower floating height, and even a minute fluctuation of floating height affects the characteristics. It has become increasingly difficult to maintain a constant height of floating in the scope necessary for excellent characteristics merely by increasing the load of the head slider or reducing the area of the air bearing surface without taking into considerations the difference in peripheral speed between the outer and inner peripheries of the magnetic disc.
Accordingly, an object of this invention is to provide a hard disc drive device which can minimize the difference in the floating heights of a head slider between the outer and inner peripheries of a magnetic disc, and stably retain a constant height from the disc over the whole recording/ reproducing area in the radial direction of the magnetic disc so as to realize operation of the head slider with the minimum height of the floating, and especially to provide a magnetic head device with constant head floating height which is to be incorporated in said drive device.
This invention provides a magnetic head device with constant head floating height wherein a head slider having an air bearing surface extending along the longitudinal direction of a head arm is fixed on an end of a suspension means (a load beam) extending from the head arm, and the distance between the rotational center of said head arm and the center of said slider and the position of the rotational center of the head arm are set to satisfy the following relation:
0xe2x89xa6(D-L)mmxe2x89xa6(0.6 Wxe2x88x924.4)mm
wherein the distance from the rotational center of said head arm to the center of the magnetic disc is expressed as D (mm), the distance from the rotational center of said head arm to the center of said head slider as L (mm), and the radial width of the recording area of said magnetic disc as W (mm).
In the magnetic head device with the structure according to this invention, the difference between the length from the head arm to the suspension means and the length from the rotational center of the arm to the center of the magnetic disc is set to satisfy the relation as expressed above, so that the longitudinal direction of the air bearing surface of the head slider may gradually approximate the tangent of the recording track of the magnetic disc as the head slider moves from the outermost periphery to the innermost periphery of the disc. Therefore, the air pressure between the air bearing surface of the head slider and the magnetic disc would not become too large on the side of the outermost periphery of the disc where the peripheral speed is maximum, or too small on the side of the innermost periphery thereof where the speed is minimum. As a result, fluctuations in the floating height of the magnetic head between the inner and outer peripheries of the magnetic disc become almost null, and stable floating can be secured. When this device was tested on magnetic discs of various sizes, it was confirmed that the difference between the maximum height and the minimum height was less than 1 xcexcin over the whole recording area. As the floating is made constant, the characteristics are stabilized. Moreover, a magnetic head device with minimum head floating height is realized.